[The early church] were continually devoting themselves to the apostles' teaching and to fellowship, to the breaking of bread and to prayer.
Acts 2:42 NASB
Being alone with God in the prayer closet is vital. However, praising, praying and interceding in agreement with other believers ought to be practiced regularly.
This is what the early church and the apostles did (see also Acts 4:23-31).
Families should pray together. Husbands and wives should pray together. Churches and church groups should pray together. Christian friends should pray together.
It is important to remember that regardless of who prays with who, time alone with God must never be replaced or neglected.